JPH09270429A - Ball-array substrate and array head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball-array substrate and array head which form ball bumps more reliably than conventional bump formation by improving positional precision in bump formation. SOLUTION: An array substrate l, for arraying micro conductive balls 3 at positions corresponding to electrodes 4 on a semiconductor device or a substrate, comprises a glass substrate having array holes 2 having a diameter smaller than that of the micro conductive balls 3 (preferably, 1/3 ⊖ (diameter of array hole/diameter of micro conductive ball) ⊖ 4/5). Preferably, the array substrate 1 is a photosensitive glass substrate having a thickness of 0.3mm ⊖thickness of array substrate <1.0mm. An array head includes the array substrate 1, and array-substrate holding means having pressure reducing spaces 7 and 8 on its surface opposite to the surface of the array substrate 1 holding the micro conductive balls 3. The positional precision of ball arrayal is greatly improved by improving precision of hole positions of array holes to suck-hold the micro conductive balls 3 and precision of hole shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an array substrate and array head of minute conductive balls for forming bumps from a large number of minute conductive balls on an electrode portion such as a semiconductor element or a substrate. .

[0002]

2. Description of the Related Art In a manufacturing process of a semiconductor device, a fine conductive ball is used as a method for connecting an electrode portion (electrode pad) of a semiconductor element to an electrode portion of a printed wiring board or an inner lead of a TAB tape. There is known a method of joining the two via a bump formed in (a so-called ball bump method). When forming the bumps, an array substrate is used which has a large number of array holes corresponding to the electrode portions of the semiconductor element, and the minute conductive balls are arrayed in each array hole.

In forming the bumps, for example, when forming bumps on the electrode pads of the semiconductor element, the array substrate is placed downward by a method such as vacuum suction to attract and hold the minute conductive balls in the array holes. In this state, it is transported to the bump bonding stage. Then, bumps are formed by thermocompression-bonding the minute conductive balls to the electrode pads on the bonding stage. Alternatively, when forming bumps made of a low melting point metal on the electrode part of a printed wiring board or the like,
In general, a flux is previously supplied to the electrode part, and the fine conductive balls are arranged on the electrode part and then reflowed.

A conventional arraying substrate is disclosed in, for example, Japanese Patent Laid-Open No.
As described in JP-A-250643, a metal such as stainless steel or a ceramic is used as a material, and each array hole is formed by precision electric discharge machining, laser irradiation, electroforming, etching, or the like.

[0005]

However, when the array substrate is made of a metal such as stainless steel, due to a large thermal expansion coefficient difference with Si, thermal expansion of the array substrate due to heat at the time of bonding causes the electrodes to be arranged during ball alignment. However, there is a problem that the position of the array holes is displaced. Further, in the method of making holes by laser irradiation and electric discharge machining, there is a problem that the meat around the arrayed holes rises and variations in height of the suction balls and deterioration of suction performance occur.

Further, in the conventional array drilling process, the hole diameter is 1
If it is less than 00 μm, it is difficult to perform precise processing with a general-purpose device, and if a hole diameter of less than that is required, the method of narrowing the hole diameter by plating after hole processing is adopted, which increases the number of manufacturing processes. There were problems such as non-uniform pore size. In addition, the holes are not aligned in a perfect circle, so the ball positions are slightly deviated and the balls are mounted when the bump formation target (semiconductor element, TAB inner lead, printed wiring board, etc.) has a fine pitch. There was a problem such as poor position accuracy.

An object of the present invention is to provide a ball array substrate and an array head which can improve the accuracy of the bump formation position and can form the ball bumps more reliably than before.

[0008]

The ball-arranged substrate of the present invention has a diameter smaller than that of the micro-conductive balls in order to arrange the micro-conductive balls at positions corresponding to the electrodes of the semiconductor element or the substrate. An array substrate made of glass provided with array holes, wherein the diameter of the array holes on the side of the array holes on which the micro conductive balls are arrayed is 1/3 ≦ (array Hole diameter / micro conductive ball diameter) ≦ 4 /
5 is a glass array substrate that satisfies the condition 5 and the thickness of the array substrate satisfies 0.3 mm ≦ the thickness of the array substrate ≦ 1.0 mm.

In the ball array substrate of the present invention,
It is a glass array substrate characterized in that the glass array substrate is made of photosensitive glass.

Alternatively, the arraying head according to the present invention comprises the minute conductive ball arraying means for arraying and holding the minute conductive balls under the arraying substrate, and the means for holding the arraying substrate. An array substrate holding means having a reduced pressure space provided on the side of the array substrate opposite to the surface holding the minute conductive balls is included.

According to the present invention, the accuracy of the ball array position can be remarkably improved by using glass as the material of the array substrate and increasing the accuracy of the opening position and hole shape of the array holes for sucking and holding the balls. .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a ball array substrate and an array head according to the present invention will be described below with reference to the drawings.

The array substrate of the minute conductive balls of the present invention is
For example, as shown in FIG. 1, it has a plurality of array holes formed so as to correspond to the electrode parts of the semiconductor element or the substrate, and the minute conductive balls to be formed in the electrode part of the semiconductor element are arranged in the array holes. It can be held by suction or the like. In particular, by using glass, which has a coefficient of thermal expansion lower than that of metal such as stainless steel and has a coefficient of thermal expansion close to that of Si, as a material for the substrate, it is possible to reduce the positional deviation between the minute conductive balls and the electrode portion even at the time of high temperature thermocompression bonding. You can

When an array substrate made of glass is used, for example, when pressure is applied excessively and pressure is applied to the balls to dig into the openings of the array substrate, the array substrate is immersed in a solution that dissolves a metal such as acid or alkali. This makes it possible to easily remove the fine metal balls that have bitten. In the case of an array substrate made of metal, since the array substrate itself is a metal, it is difficult to completely remove the fine balls that have melted into the dissolution liquid and invaded.

The thermal expansion coefficient of the glass array substrate of the present invention is 1
˜100 (× 10 ⁻⁷ / ° C.), preferably a thermal expansion coefficient of Si (about 40 × 10 ⁻⁷ / ° C.) to about twice that of 20 to 90 (× 10 ^{− 7} / ° C.), the positional displacement during the array can be made considerably smaller than that of the metal array substrate. In addition, among the glasses, particularly by using photosensitive glass, fine array holes having a good hole shape are opened with high positional accuracy, and ball bumps have a fine pitch (pitch of 300 μm or less, particularly 100 μm or less).
Also in the above, it can be formed without displacement.

Further, when the photosensitive glass is used, since exposure is performed using a mask as described later, holes can be formed at one time, so that the cost of the array substrate can be extremely reduced. This effect is more than 100 pins (especially 3
It becomes remarkable when an array substrate having 100 pins or more) is manufactured. That is, in the case where holes are formed one by one by electric discharge machining or the like, if even one fails, the process is restarted from the beginning, and the yield of substrate fabrication is reduced. In addition, the array substrate of the present invention can easily be formed with an alignment mark at any place and in any number, and can be used for alignment with the electrode portion on which the bump is formed.

The photosensitive glass of the present invention is made of, for example, SiO ₂
-Al ₂ O ₃ -LiO-based glass as a base, and a glass containing Ag, Au, Cu, etc. as a photosensitive metal. Further, CeO ₂ or the like, which is a photosensitizer, may be added if necessary. Both sides of this photosensitive glass are polished, and a mask having an array hole opening pattern drawn at a desired position (corresponding to an electrode position of a semiconductor element or the like) is placed on one surface of the polished glass surface. After that, ultraviolet rays are radiated from above the mask to expose the glass in the opening portion to light. The mask is removed, and appropriate heat treatment is performed to crystallize the exposed portion. The crystallized portion is dissolved with acid to form arrayed holes.

The opening position is within ± 5 μm (preferably ± 3
By using the array substrate of the present invention processed with an accuracy of (μm or less), a position within ± 5 μm (preferably within ± 3 μm) from the center of the array hole and the corresponding center of the Al electrode pad or the like on the semiconductor element. It is possible to form bumps with high precision.

In the above method, the exposed portion is easily etched by acid to form the opening. However, by selecting the type of the photosensitive glass, the exposed portion is exposed to acid to etch the portion other than the opening portion with acid or the like. A similar opening can be formed by making it difficult.

The array substrate of the present invention can also be used by being attached to a head to which pressure or heat can be applied when the balls are arrayed. In this case, the array substrate needs to have a certain thickness in order to have a strength capable of withstanding the pressure at the time of joining. If this thickness is too thick, it will be difficult to dissolve with an acid or the like. The present inventors have studied using array substrates of various thicknesses, and as a result, in order not to make the openings nonuniform,
It has been found that a thickness of 1.0 mm is suitable.

The thickness of the glass substrate is limited as described above. For example, when the thickness of the array substrate was less than 0.25 mm and a force of 5 kg was applied to the array substrate, the array substrate could not withstand the applied pressure and a phenomenon of cracking of the array substrate occurred at a rate of about 10% with respect to the number of pressurizations. When the thickness is set to 0.3 mm, the array substrate can be used for production without any damage even when the pressure is applied 10,000 times. On the other hand, when the thickness is 1 mm or more, when glass is melted by etching or the like to open,
If the etching time is long and the accuracy of the hole diameter is also long, it is difficult to make the number of holes uniform. Therefore, the thickness of the glass array substrate is preferably 0.3.
The present invention has revealed that it is necessary that mm ≦ thickness of array substrate ≦ 1.0 mm.

When applying the fine balls to the array substrate, it was necessary to optimize not only the thickness thereof but also the aperture diameter required for suction holding through various experiments. If the diameter of the array holes is simply smaller than the diameter of the minute conductive balls, the success rate of array by suction cannot be secured. If the ratio of the diameter of the arrayed holes to the diameter of the minute conductive balls is less than 1/3, the suction efficiency will decrease. In the study of the present invention, for example, 80 μmφ
When 500 solder balls are suction-held, the success rate of suction-holding is 80 to 87% when the hole diameter of the array substrate is 20 μm or less.
Therefore, when the pore diameter was set to 25 μm or more, the suction holding success rate of 95% or more could be secured.

Further, if the ratio of the diameter of the arrayed holes to the diameter of the minute conductive balls exceeds 4/5, the balls will bite into the holes due to the pressure applied when the minute balls are transferred to the electrodes. It turned out by various experiments. For example 40 μm
When gold balls with a diameter of 34 μm are held by an array substrate and pressure is applied on the electrodes with a force of 20 g per ball, 52 of the 300 balls dig into the holes of the array substrate, resulting in defective ball bonding to the electrodes. Occurred. When the pore size was set to 32 μm, no bite occurred. Therefore, the hole diameter is 1 /
It was found for the first time in the present invention that the condition of 3 ≦ (diameter of array holes / diameter of minute conductive balls) ≦ 4/5 needs to be satisfied. When holes are formed by electric discharge machining on an array substrate made of metal such as stainless steel, such a tendency does not clearly appear because the meat rises around the openings.

Some examples of array hole shapes in the array substrate of the present invention are shown in FIG. The surface on which the balls are arranged is the surface. In FIG. 2, the arrangement of holes on the front and back sides is the same (A), the diameter of the front surface is smaller than that of the back surface (B), and the diameter of the front surface is opposite to that of (B). The one that is larger than the back surface is (C). Also,
The type shown in (A) was machined to increase the surface pore size, and the surface opening edge was dropped (D),
A shape obtained by similarly processing the back surface of the type shown in (D) to the back surface has a shape in which the types of (E), (B) and (C) are mixed. (F) indicates that the hole diameter of the portion is wide and the hole diameter becomes smaller toward the inside of the array substrate.

Here, the type (B) has a large diameter on the pressure-reducing side opposite to the ball suction surface, and since the balls of the array head holding the array substrate are sucked, the suction system can be easily manufactured ( In the portion of the array head that holds the array substrate, for example, it is necessary to form a groove pattern for supplying a vacuum corresponding to the holes in the array substrate, and if the hole diameter or the hole pitch is narrow, its formation becomes difficult. Come).

In the type shown in FIGS. 2D, 2E and 2F, the array holes may be processed by either an acid etching method or mechanical polishing. In that case, a smooth curve may be used instead of a linear taper. In the type of FIGS. 2E and 2F, the hole diameters of the front surface and the back surface of the array substrate may be the same or may be the same, but the hole diameter of the minimum hole diameter portion for sucking and holding the balls on the back surface is equal to the ball diameter. 1/3 to 4/5 is desirable.

In addition to the arrangement of gold balls on the chip described in the following embodiments, the arrangement substrate according to the present invention also has an arrangement of gold or solder balls on the electrodes of a film carrier such as TAB.
Alternatively, it can be applied to the arrangement of gold or solder balls on the electrodes of the printed wiring board. When forming bumps with solder balls, flux may be supplied to the electrode portions in advance.
Used together with a head including an array substrate made of a glass substrate according to the present invention, and a holding means provided with a pressure-reducing space for holding the array substrate and minute conductive balls on the side opposite to the surface holding the balls. Then, the ball bump can be formed with extremely high accuracy.

[0028]

EXAMPLE FIG. 3 shows a method of manufacturing micro conductive ball bumps using an array substrate according to the present invention. A detailed description will be given below with reference to the drawings. In FIG. 3A,
The array substrate 1 of the type shown in FIG. 2B is fixed to the array substrate fixing jig 9 made of stainless steel by depressurizing the array substrate suction depressurizing space 8. The minute balls 3 having a diameter of 60 μm and containing Au as a main component are collectively sucked and held by depressurizing the ball suction depressurizing space 7 of the array substrate fixing jig 9.

The array substrate 1 has 30 μ which is ½ of the ball diameter.
An array hole 2 of m diameter is opened. The balls 3 are from the rear surface of the array substrate 1 to the ball suction decompression space 7 of the array substrate fixing jig 9.
It is held in this array hole 2 by suctioning under reduced pressure.

In FIG. 3B, the array substrate 1 is moved onto the semiconductor element 5, and the balls 3 and the electrode pads 4 are aligned with each other. Here, if an alignment mark formed on the array substrate is used, quick alignment is possible.

In FIG. 3C, the held ball 3 is lowered toward the semiconductor element electrode pad 4 placed on the support 6. And 10 to 30 per ball
Pressurize with a load of g.

In FIG. 3 (D), the balls 3 are joined together and the reduced pressure space for ball suction 7 is brought to atmospheric pressure, and the array substrate 1
To rise.

In this example, as described above, this array substrate 1
Is adsorbed by decompressing the array substrate suction decompression space 8, but an integrated ball suction / transfer head in which the array substrate 1 is fixed to the array substrate fixing jig 9 without the array substrate suction decompression space 8. May be used. Further, the array substrate fixing jig 9 of the present invention is provided with a heating mechanism, so that it is possible to raise the temperature of the balls to join them.

In the above embodiment, the minute conductive balls 3
When sucking and holding, the excessive balls were not sucked due to the suction leakage (removal) or the air leakage due to the defective hole shape. Semiconductor device 5 installed on semiconductor device support 6
Is heated to 300 to 500 ° C. The bumps are formed by forming Al and an Al-Au-based alloy with the electrode material Al and joining them, and there is no chipping. The positional deviation of the array substrate of the present invention due to the influence of heat when forming bumps was within ± 3 μm. The variation in bump height was within ± 2 μm. Moreover, even if such a semiconductor device with bumps was transported, the bumps did not fall off.
Furthermore, when a semiconductor element was joined to the inner lead of the film carrier using this bump, it was confirmed that there was no drop of lead.

When ball bumps were formed using an array substrate of stainless steel in which array holes were formed by electric discharge machining under the same bonding conditions as described above, a displacement of ± 10 μm or more occurred. Further, there was a variation in bump height of ± 7 μm. If the reduced pressure space for ball suction provided in the array substrate fixing jig is large and the contact area with the array substrate fixing jig around the array holes is extremely small, the array substrate may not be able to withstand the pressure during bonding. In order to prevent the destruction of the array substrate, it is desirable that the reduced pressure space for ball suction has a groove shape 10 to 100 times the diameter of the array holes.

However, when the balls are attracted and arranged in a lattice in a plane arrangement, the arrangement holes 1 are formed in a lattice form in the arrangement substrate 1 as shown in FIGS. 4 (A) and 4 (B). It is necessary to increase the contact area between the array substrate fixing jig 9 and the array substrate 1 by providing the columnar projections 10 in the ball suction decompression space 7a as shown in FIG. As another method for increasing the contact area, a porous material may be used for the ball suction decompression space 7a, or a porous material may be used for the array substrate fixing jig 9 itself.

[0037]

As described above, according to the present invention, the array substrate is made of glass and the array holes for sucking and holding the balls are formed by the array substrate of minute conductive balls or the array head using the array substrate. Since the precision of the position and the shape of the holes is improved, the precision of the ball arrangement position is remarkably improved, and the minute conductive bumps can be formed on the electrodes of the semiconductor chip, the film carrier, the printed wiring board and the like with high precision.

[Brief description of drawings]

FIG. 1 is an external perspective view of an array substrate according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an example of the shape of array holes in the array substrate of the present invention.

FIG. 3 is a diagram showing an example of a method of forming a minute conductive ball bump using the array substrate of the present invention in the order of steps.

FIG. 4A is an external perspective view of an array substrate showing an example of a grid-like array hole of minute conductive balls in the present invention, and FIG. 4B is a diagram showing the array substrate and a jig for fixing the array substrate. .

5A is a cross-sectional view of an array substrate showing an example of a grid-like array hole of micro-conductive balls in the present invention, and FIG. 5B is a P arrow view of FIG.

[Explanation of symbols]

 1 Micro Conductive Ball Array Substrate 2 Array Hole 3 Micro Conductive Ball 4 Electrode Pad 5 Semiconductor Element 6 Support 7 and 7a Decompression Space for Ball Suction 8 Decompression Space for Array Substrate Suction 9 Array Board Fixing Jig 10 Columnar Protrusion

Claims (3)

[Claims] 1. An array substrate made of glass provided with array holes having a diameter smaller than the diameter of the minute conductive balls in order to arrange the minute conductive balls at positions corresponding to the electrodes of the semiconductor element or the substrate. The diameter of the array hole on the side where the micro-conductive balls of the array holes are arrayed is 1/3 ≦ (diameter of array hole / diameter of micro-conductive ball) ≦ 4 /
5. An array substrate of minute conductive balls, wherein the array substrate satisfies the condition 5 and the array substrate thickness satisfies 0.3 mm ≦ array substrate thickness ≦ 1.0 mm. 2. The array substrate of micro-conductive balls according to claim 1, wherein the array substrate made of glass is made of photosensitive glass. 3. The array substrate according to claim 1 or 2, the micro-conductive ball array means for array-holding the micro-conductive balls under the array substrate, and the array substrate. An array substrate holding means provided with a reduced pressure space on the opposite side of the array substrate from the surface holding the array of minute conductive balls.